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| United States Patent |
6,199,713
|
|
de Vries
|
March 13, 2001
|
Reusable container having a protective coating and method for the recovery
thereof
Abstract
A reusable container, in particular for environmentally harmful substances,
such as paint, adhesive and the like, comprises a container body (1), the
inside and/or outside of which is provided with a protective coating (7,
6) which consists of a material which is solvent-resistant at application
temperature and at a raised temperature is soluble or softenable in a
solvent, preferably water. This material is preferably polymethyl
methacrylate.
| Inventors:
|
de Vries; Carl Maria (Nieuwegein, NL)
|
| Assignee:
|
Henkel Nederland B.V. (NL);
B & R Recycling B.V. (NL)
|
| Appl. No.:
|
014537 |
| Filed:
|
January 28, 1998 |
| Current U.S. Class: |
220/495.02; 220/23.9; 220/23.91; 220/62.15; 220/62.22 |
| Intern'l Class: |
B65B 003/00 |
| Field of Search: |
220/62.11,62.22,62.14,495.02,23.91
|
References Cited
U.S. Patent Documents
| 3085375 | Apr., 1963 | Harrison | 53/442.
|
| 3652333 | Mar., 1972 | Warren | 427/96.
|
| 4122973 | Oct., 1978 | Ahern | 220/495.
|
| 4800845 | Jan., 1989 | Budd | 220/495.
|
| 5051284 | Sep., 1991 | Johansson et al. | 428/34.
|
| 5492242 | Feb., 1996 | Gall | 220/495.
|
| Foreign Patent Documents |
| 4102326 | Jul., 1992 | DE.
| |
| 0468244 | Jan., 1992 | EP.
| |
| 0579106 | Jan., 1994 | EP.
| |
| 9105714 | May., 1991 | WO.
| |
Primary Examiner: Sewell; Paul T.
Assistant Examiner: Arnold; Troy
Attorney, Agent or Firm: Ostrolenk, Faber, Gerb & Soffen, LLP
Parent Case Text
CROSS-REFERENCE TO RELATED APPLICATIONS
This is a continuation of International Application PCT/NL95/00262, with an
International filing date of Jul. 28, 1995.
Claims
What is claimed is:
1. Reusable container for environmentally harmful substances, comprising a
container body having an outside and an inside, an inner protective
coating on the inside of the container body and an outer protective
coating on the outside of the container body, wherein at least the outer
protective coating is made of a material, which is solvent-resistant and
water-resistant at ambient temperature and which is water-soluble or
water-softenable at a raised temperature above ambient.
2. Reusable container according to claim 1, wherein the material of at
least the outer protective coating is selected from acrylic-based polymers
or resins.
3. Reusable container according to claim 2, wherein the material of at
least the outer protective coating is transparent.
4. Reusable container according to claim 2, wherein the material of at
least the outer protective coating is polymethyl methacrylate.
5. Reusable container according to claim 1, wherein the protective inner
coating is immovably connected to the container body.
6. Reusable container according to claim 1, wherein the protective inner
coating is placed loose in the container body.
7. Reusable container according to claim 1, wherein the outer coating
overlaps the inner coating on the inside of the container body.
8. Reusable container according to claim 1, wherein the protective inner
coating is made of a plastic with high resistance to mechanical stress.
9. Reusable container according to claim 8, wherein the protective inner
coating is made of polyethylene terephthalate.
10. Reusable container according to claim 1, wherein the container body is
comprised of a plastic or metal material.
11. Reusable container according to claim 1, wherein the container also
comprises a cover, the cover including an underside, at least the
underside of the cover is provided with a protective coating comprised of
a material which at ambient temperature is water-resistant, and which at a
raised temperature above ambient is soluble or softenable in water.
Description
The invention relates to a reusable container, in particular for
environmentally harmful substances, according to the preamble of claim 1.
Such a container, in particular in the form of a plastic bucket for paint,
adhesive and the like, is known from German Offenlegungsschrift
DE-A1-4,102,326.
After use, containers for environmentally harmful substances still contain
a residue of the contents, while the outside is often covered with spilt
residues of the environmentally harmful substances. These substances and
containers soiled therewith are generally regarded as chemical waste, and
must therefore be collected and disposed of separately. Under current
legislation in this field, the percentage by weight of the environmentally
harmful substances relative to the container is an important factor in
determining whether or not the container is to be regarded as chemical
waste.
In modern society the authorities are seeking to make the producer of
environmentally harmful materials or products responsible for this
disposal after use. In the case of e.g. a paint manufacturer it means that
this manufacturer may be obliged to take back and collect used paint cans
and buckets and to ensure environmentally acceptable processing thereof.
In order to limit this quantity of waste for processing, it is in the
interest of such a manufacturer only to dispose of the environmentally
harmful substances, while the container body (e.g. cans or buckets) is
available for reuse.
In the case of the bucket known from DE-A-4,102,326 a pull-off film is used
as the protective coating on the inside and/or outside of the container
body, said film being applied thereto with or without the use of an
adhesive. After use, the protective coating with residues is pulled off
the bucket. Ethylene vinyl acetate is mentioned as an example of a
suitable film. Such buckets can be manufactured by heating the container
body to a high temperature, e.g. 100.degree. C., and then placing a
preformed film of the protective coating therein under pressure. If both
the container and the film are made of a thermoplastic material, the
desired adhesion can be obtained by using pressure and heating.
A disadvantage of such a coating, which can be removed from the container
body by pulling it away, is the risk that the coating will tear while it
is being pulled away, even in the case of a relatively thick 0.2 mm film.
If the container body is a complex shape, for example if it has a flanged
top edge, this risk is high. It can mean that soiling of the container
body itself can still occur, which is undesirable. This problem has
already been recognized in DE-A-4,102,326, where it is proposed that the
coating should be provided with a loop which is connected to a
reinforcement strip placed in the coating, as a result of which the chance
of tearing when the coating is being pulled away is counteracted. However,
the disadvantages here are that the costs of the coating itself are
increased, and its manufacture becomes more complicated and consequently
more expensive.
A further disadvantage of this known container is that such a removal step
of pulling the coating away is labour-intensive, certainly if the coating
consists of several parts. Besides, mechanization of such a method is not
easy to achieve. Finally, after the removal of the pull-off film, the
container body will generally have to be degreased before a new peel-off
coating can be applied.
WO-A-91/05714 discloses a container for Hazardous substances, in particular
agrochemicals, comprising an outer shell made from compressed fibrous
material, having an associated barrier of a polymeric material and an
inner water soluble or water dispersible envelope for containing the
contents. This envelope together with the contents can be tipped into
water for further processing the contents.
EP-A-0 468 244 discloses a reusable plastic container, comprising a
container body, of which the inside is provided with a plastic coating
layer, which is not soluble in the intended contents of the container and
which is soluble in an aqueous detergent solution. The difference in
solublity of the coating material in the intended contents and the aqueous
detergent solution is related to the difference of the acidity of the
contents, respectively the detergent solution.
The object of the invention is to provide a reusable container to which the
protective coating can be applied in a simple manner, and from which it
can be removed and collected separately from the container body in a
simple manner, and the costs of which are relatively low.
The features of the reusable container of the abovementioned type according
to the invention are defined in the characterizing portion of claim 1.
In the context of the invention ambient temperature should be understood as
the usual temperature at which the contents of the container are stored,
transported and processed. Solvent-resistant should be understood as
meaning that the coating material is resistant to the contents of the
container and to solvents which are normally used for processing the
contents. The protective coating will not dissolve, react or otherwise
deteriorate at the usual processing temperature under the influence of the
contents or under the influence of means used for processing the contents.
Raised temperature should be understood as meaning a temperature which is
higher than the normal processing temperature.
One advantage of the container according to the invention is that the
protective coating can be removed in a simple manner using a heated
solvent, preferably water. Such removal can be carried out quickly and
completely and is simple to automate. Examples of this are washing with a
heated solvent, immersion in a bath of such a solvent or spraying with a
solvent under pressure. The coating material removed, with residues, can
be separated from the solvent using known purification techniques or, if
the concentrations of film-forming material and residues in water are
sufficiently low (lower than the permissible concentration limits for
discharging into the sewer), the water can be discharged directly into the
sewer. Such a coating can advantageously be applied very thinly (of the
order of magnitude of micrometers) to the container body, while the
desired physical properties of the protective coating can still be
obtained. This means that the quantity of waste material for disposal,
coming from the coating itself, can be kept small.
After use of the container, both the remainder of the contents and all
residues of environmentally harmful substances which have been spilt or
are otherwise adhering to the outside of the container body can be removed
with the coating, so that the container body is completely clean and is
thus suitable for reuse through the application of a new coating thereto
and subsequent refilling of the container. Such removal of the protective
coating is easily carried out by the manufacturer himself, who takes back
the containers from the user after use. After removal of the protective
coating, it is possible to apply a simple cleaning operation, e.g. washing
and drying, if such cleaning is considered necessary.
The demands to be made of the coating material include chemical resistance,
for example to the environmentally harmful substances, as already stated
above, and sufficient strength to prevent damage during use. Such damage
can occur if, for example, the contents of the container have to be
stirred or mixed in some other way before being processed.
Preferred materials suitable for use as protective coating materials
according to the present invention include acrylic-based polymers or
resins.
It is also advantageous for the outer coating to be transparent. This makes
it possible to print the outside of the container body once, for example
with a brand name and/or data concerning the contents of the container,
without such data having to be applied to the outer coating. Since this
coating part is transparent, the outside of the container body, and
consequently these data, always remain visible.
A material which is particularly preferred is polymethyl methacrylate
(PMMA). PMMA is a clear, colourless, transparent plastic having a high
softening point, good impact strength and good weather resistance. This
material can also be applied as a thin film to the container body by
conventional techniques such as pouring, immersion and/or spraying. The
low relative density of PMMA, combined with the low thickness of the film
layer has a beneficial effect on the quantity of waste to be processed.
PMMA softens at 70.degree. C. and at this temperature will come away from
the container body and form a gelatinous sheet which is simple to remove
from the solvent, for example water. A simple separation of the PMMA sheet
from the water is possible through the fact that this sheet floats on the
water. PMMA is also resistant to many aqueous, inorganic reagents,
including dilute bases and acids, and to normally used organic solvents.
The protective inner coating of the container can be in the form of a bag
or pre-shaped film placed loose in the container. Said protective inner
coating can also be immovably connected to the container, in order to
reduce the risk of damage during use. Moreover, the outer coating and the
inner coating can be of separate parts, which is advantageous if only the
inner coating needs to be removed, because the outside of the container
has not been soiled with the contents thereof. In order to protect the
container completely, in such a case the inner and outer coating join up
with each other in a sealing manner.
Compared with the method of manufacture described in DE-A-4,102,326, which
is in two steps, namely forming a pre-shaped film and then fixing said
film in the container body, the present container has the advantage that
the protective coating can be applied to the container body. in one step.
In certain cases, depending on the application, it may be necessary to
select a different material with better resistance to mechanical stress
for the protective inner coating. Examples of this are polypropylene,
polyethylene terephthalate and comparable inert plastics. A preferred
combination is an outer coating of PMMA and an inner coating of
polyethylene terephthalate (PET). The PET coating can be placed loose in
the container or can be fixed to the container by means of adhesive. The
outer coating preferably overlaps the inner coating at the inside of the
container over a distance large enough to prevent undesirable pollutants
from penetrating between the inner coating and the inside wall of the
container. The overlap at the inside of the container is better from the
point of view of weight and adhesion than an overlap at the outside,
because the soluble or softenable material according to the invention is
easier to apply to the edge (flange) of the container than the more rigid
PET material.
The nature of the container body itself is not critical for the invention,
but it will usually be made of plastic or metal.
Secondly, the invention relates to a method for recovering reusable
containers according to the invention, which method is characterized in
that the container is subjected to a treatment with a solvent, preferably
with water, at elevated temperature, the protective coating is removed
from the container body, and the container body and the solvent containing
the protective coating are separated from each other.
If a container with a PET inner coating and a PMMA outer coating or
comparable materials is used, the PET inner coating with the residual
content is first removed, before the treatment with solvent is carried
out. The PET inner coating and the residual contents can be separated from
each other by, for example, cryogenic techniques.
The invention will be explained below with reference to the appended
drawing, in which:
FIG. 1 is a cross-section of an embodiment of a container according to the
invention;
FIG. 2 is a top view of a closing element for the container of FIG. 1;
FIG. 3 is a cross-section along the line I--I of the closing element shown
in FIG. 2; and
FIG. 4 is a cross-section of a second embodiment of a container with cover
according to the invention.
FIG. 1 shows a container according to the invention which comprises a
container body 1. The container body 1 comprises a bottom 2 and a wall 3
rising from the bottom, and an opening 4 lying opposite the bottom 2. The
container body 1 comprises an edge 5 at the top side of the wall 3 beside
the opening 4. The coating, indicated in general by reference number 6, in
the embodiment shown here consists of an inner coating 7 and an outer
coating 8, both of which are applied by spraying PMMA onto the container
body 1, and which are immovably connected thereto. For reasons of clarity,
the coatings in the figure are shown exposed. The inner coating 7 overlaps
the outer coating 8 at the outside of the container body at the position
of the edge 5, so that the two coatings 7 and 8 join up with each other in
a sealing manner. As a result of this design of the coating parts 7 and 8,
the container body 1 is completely protected.
In the case of the container shown in FIG. 1 the protective coating is
formed in two parts, in order to make it possible to remove only the
soiled inner coating 7 after use, by means of a solvent at high
temperature, while the outer coating 8, if it is not soiled, remains
behind on the container body 1. The stream of waste to be processed can be
limited further in this way. It is also possible to manufacture the inner
and outer coating in different thicknesses, because the physical demands
made of the coating are different for the two positions. Optimum
adaptation to these demands and to the contents of the container can
easily be made by the person skilled in the art.
As shown in FIG. 1, the outside of the container body 1 comprises a
protuberance 9 in the vicinity of the edge 5. The function of this
protuberance 9 is explained further with reference to FIGS. 2 and 3.
In order to be able to seal the container body 1, which is provided with a
protective outer coating 8, without damaging said protective coating, a
closing element 10, in the form of an annular locking element, can be
used. A top view of such a closing element is shown in FIG. 2. The closing
element 10 is pushed from the underside onto the container body 1 having
the outer coating 8 until it passes the protuberance 9. The protuberance
9, in combination with the edge 5, ensures the positioning of the closing
element 10. The locking element 10 is in a tight fit around the container
body 1.
FIG. 3 shows in detail a section along the line I--I of the closing element
of FIG. 4. The annular locking element 10 is provided with a clamping
element 11 on the inside. The clamping element 11 is preferably made of a
slightly elastic material, so that it is easily pushed over the
protuberance 9. The shape of the clamping element 11 is adapted to the
shape of the bottom edge 5. If the bottom edge 5 is a round shape, as
shown in FIG. 1, the part of the clamping element 11 of the closing
element 10 which is in contact therewith, will also be a round shape.
In the section of the closing element 10 shown, the outer periphery thereof
is provided with a threaded element 12, on to which a screw cover (not
shown) can be screwed in a simple manner, in order to shut off the opening
4 of the container. As can also be seen from this figure, the closing
element 10 has on the underside of the element 12 a flange 13, to which a
handle 14 is fixed. In this way the container is easy to transport by the
end user, while the protective coating remains intact.
It will be clear that if the container body at the opening side 4 does not
have a bottom edge 5 against which the closing element 10 can rest in a
tight fit, it is possible to provide two protuberances on the outside,
between which the closing element is positioned. This makes it possible to
shut off the container in a similar way to that described above, by means
of a cover which is screwed onto the closing element. Another example for
shutting off the opening of the container body is a snap-on cover, which
is snapped over the closing element. In this case it is, of course, not
possible to provide the closing element with screw thread.
As will be understood by the person skilled in the art, the snap-on or
screw cover can also advantageously be provided with a protective coating
of a material which at ambient temperature is solvent-resistant, and which
at raised temperature can be dissolved or softened in the solvent.
A second embodiment of a reusable container according to the invention is
shown in FIG. 4. A container body 21 comprises a bottom part 22 and an
upright side wall 23 having an opening at the top side of the container
body 21 indicated by reference number 24. The opening 24 is bounded by a
peripheral edge 25 at the top side of the side wall 23. The container body
21 is completely covered by a coating 26, consisting of two different
materials. An inner coating 27 of PET protects the inside of the container
body 21, and a PMMA coating 28 protects the entire outside of the
container body 21. As can be seen clearly from this figure, the outer
coating 28 overlaps the inner coating 27 on the inside of the container
body 21 over a certain distance (indicated by arrow 29), in order to
prevent the inside of the container body from becoming soiled. The
container also comprises a snap-on lid 30, which is provided with a
protective PMMA coating on the underside thereof.
When the protective coatings are being removed, the PET inner coating with
the residual contents will first be removed in a conventional manner,
following which the PMMA coating of the cover and the container body is
removed using water at a temperature of, for example, 60-70.degree. C.
This coating forms a gel in the water, which gel floats on the water and
is thus easily separated. The PET coating with the remainder of the
contents is subjected to a thermal treatment with liquid nitrogen, during
which the PET coating is cooled so much that these different materials
come apart. The PET pieces are collected and can be reused.
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